1. Field of the Invention
This invention pertains generally to ink fountains utilized in offset printing apparatus, and more specifically to a control apparatus for adjusting the position of ink keys utilized in ink fountains.
2. Description of the Background Art
In the area of offset printing apparatus, ink fountains are generally used. Contained within the typical ink fountain is an inking roller (commonly called a fountain roller) and an ink metering blade (commonly called a fountain blade) which is positioned adjacent to the fountain roller. The position of the fountain blade in relation to the fountain roller is such that a gap is formed. The spacing of the gap determines the amount of ink that is applied to the fountain roller, and which in turn is transferred via other rollers to a print medium such as paper. Because it is quite common for the amount of ink transferred to vary across the print medium, it is often necessary to adjust the spacing of the gap across the length of the fountain roller. This adjustment is generally performed by operating manually or electrically controlled adjusting keys (commonly called ink keys) which are located at fixed locations along the length of the ink fountain. By moving the position of the fountain blade with respect to the position of the fountain roller, each ink key controls the spacing of the gap with respect to a particular segment, or zone, of the print medium.
Heretofore, ink keys have been of a screw-type which have required adjustment by application of rotational force or of a pusher-type which require application of a reciprocating force. Examples of devices which have been previously developed for application of rotational force are disclosed in U.S. Pat. No. 4,864,930 issued to Runyan et al. on Sep. 12, 1989; U.S. Pat. No. 4,669,382 issued to Jentzsch et al. on Jun. 2, 1987; U.S. Pat. No. 4,709,635 issued to Kubert et al. on Dec. 1, 1987; and U.S. Pat. No. 4,803,923 issued to Kenichi on Feb. 14, 1989. Examples of devices which have been previously developed for application of reciprocating force are disclosed in U.S. Pat. No. 4,711,176 issued to Michel on Dec. 8, 1987; and U.S. Pat. No. 4,829,898 issued to Wieland on May 16, 1989. Examples of devices which have been previously developed using eccentric discs which are used to adjust the position of the blade are disclosed in British Pat. No. 2,132,139 issued to Albert on Jul. 4, 1984; and U.S. Pat. No. 4,729,312 issued to Rodi et al. on Mar. 8, 1988. While the foregoing patents disclose devices which are capable of controlling the spacing of the gap between the fountain roller and the fountain blade, they do not provide for the fine incremental adjustments and repeatability of settings provided by the present invention.
The foregoing patents reflect the state of the art of which the applicants are aware and are tendered with the view toward discharging the applicants' acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, the applicants' claimed invention.